Speed responsive safety control



Jan. 25, 1966 J GREENHUT 3,231,695

SPEED RESPONSIVE SAFETY CONTROL Filed April 4, 1962 3 Sheets-Sheet 1 I3 l4or62 L F/g. 7

INVENTOR. 1 JOSEPH GREENHUT BY 44 ATTO R N EYS Jan. 25, 1966 J. GREENHUT 3,231,695

SPEED RESPONSIVE SAFETY CONTROL Filed April 4, 1962 3 Sheets-Sheet 2 F ig. 3

INVENTOR.

JOSE PH GREEN HUT mmim ATTORNEYS Jan. 25, 1966 J. GREENHUT 3,231,695

SPEED RESPONSIVE SAFETY CONTROL Filed April 4, 1962 5 Sheets-Sheet :5

INVENTOR.

JOSEPH GREENHUT ATTORNEYS United States Patent "ice 3,231,695 SPEED RESPONSIVE SAFETY CONTROL Joseph Greenhut, 2564 Saybrook Road, University Heights, Ohio Filed Apr. 4, 1962, Ser. No. 185,120 3 Claims. (Cl. 200-6139) The present invention relates to a safety control device adapted to be utilized with other apparatus to safeguard such apparatus, or the material being processed thereby, from injury due to a malfunction in the apparatus, which is reflected in an abnormal variation in the speed of a rotating member. The control device may actuate a visual or audible signal or alarm or some form of record keeping device, or it may de-energize the malfunctioning apparatus or a portion thereof, or it may exercise all or a combination of such functions in safeguarding the apparatus or the material processed thereby.

Thermo-sensitive reproduction equipment for the reproduction of paper copies is illustrative of the type of apparatus to which my invention is applicable. In such equipment, the original sheet (which is to be reproduced) is maintained in contact with 'a'sheet of heat sensitive copy paper and conveyed by a web or feed belt past a heat lamp or other suitable source of heat. The speed of the belt determines the intensity of the reproduction, as it establishes the length of time that the thermo-sensitive copy paper is exposed to the heat. customarily, regulating means are provided for adjusting the speed of the belt within limits so that the user can select the desired speed within the available range. The feed belt is driven by an electrical motor through a suitable combination of drive shaft and idler rolls. One of the problems encountered in such reproduction equipment, is slippage of the feed belt with respect to its drive shaft. This condition may arise from various causes, but most often occurs after a considerable period of use during which the belt and the drive shaft have become dirty or covered with a thin film of oil. When such slippage occurs, it may expose the papers, as well as the belt itself, to the heat source for an unduly long period of time, thus creating the possibility of injury to the papers or the belt or both, and the attendant danger of fire.

It is a primary object of my invention to provide a tion in such apparatus.

Another object of my invention, is to provide a safety control of the character described, which will cause the heat source to become inoperative when the hazardous condition occurs.

A further object of my invention is to provide a safety device of the character described, in which the rapidity of its response to the malfunctionis determined by the degree of severity of the malfunction.

Another object of my invention is to provide a safety device of the character described, in which means are provided for selectively varying the lag period or response time of the device. 7

Other objects and advantages of my invention will be apparent during the course of 'the' following description.

In the accompanying drawings forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same,

FIG. 1 is a plan-view of a safety control device embodying the features of my invention, associated with a portion of the apparatus which is to be monitored by the safety control device; v

FIG. 2 is a cross-sectional view taken as indicated on line 22 of FIG. 1, portions thereof being broken away to show certain details; i i e i 1 3,231,695 Patented Jan. 25, 1966 FIG. 3 is a cross-sectional view taken as indicated on line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view, taken in a direction opposite to that of FIG. 2, and showing a modified form of the invention;

FIG. 5 is a fragmentary sectional view taken as indicated on line 55 of FIG. 4;

FIG. 6 is a fragmentary sectional view similar to FIG. 3, but showing a further modified form of the invention. and

FIG. 7 is a view showing a modified form of circuit diagram.

Referring more particularly to FIGS. 13 of the drawings, I have shown a safety control device 10, embodying the features of my invention, associated with the idler roll 11 of a motor-driven feed belt 12, which is part of a reproduction apparatus of the general character previous ly described. An electrically energized source of heat, such as the heat lamp 13 indicated schematically in FIG. 1, is disposed in proximity to the feed belt 12, so that papers carried by the feed belt will be exposed to the heat source.

The device 10 includes a synchronous motor 14 which, through its low speed shaft 15, provides a constant reference speed for the operation of the control device. The motor shaft, in turn, is afiixed to a hub 16 by a pin 17 which extends through the hub and the shaft. Mounted on the hub 16 is a planetary reduction assembly 18, which, as here shown, consists of a conventional ball bearing having an inner race 19, which is fixedly secured to the hub, and an outer race 20, and a plurality of balls 21, carried in a ball cage 22. A pulley 23 is fixedly secured to the outer ball race 20 for rotation therewith. By means of a belt 24, the pulley 23 is connected to a pulley 25 on the idler shaft 11, thus interconnecting the two pulleys for simultaneous rotation. It will be understood that other suitable means could be employed for physically interconnecting the pulley 23 for rotation with the idler shaft 11.

An actuating member, here shown as an angular disc or ring 26, is journalled on the hub 16 for relative rotation thereto. The actuating member 26 is mechanically coupled to the ball cage 22 by means of a inter-engaging pins 27 whose head portions 28 are accommodated in the recesses or sockets 29 which are conventionally provided in the ball cage 22 in the spaces between the balls. For economy of manufacture, the actuating ring 26 is illustrated as being made of laminated stampings. However, this is merely a preferred form, and it is to be understood that the ring 26 may be provided by any suitable manufacturing process.

In some applications of the safety control device, the pins 27 are afiixed directly to the actuating ring 26. However, in the present embodiment, I have shown the clutching arrangement interposed between the carrier for the pins and the ring itself. To provide this clutching action, the pins 27 are mounted to a carrier disc 30 which is rotatably mounted within the ring [member 26. A peripheral portion of the disc 30 is cut away to provide a recess 31 which accommodates a spring 32 and a ball 33, thus providing a unidirectional ball clutch assembly of the type well known in the art. By means of the ball olutch the actuating ring 26 is coupled for rotation with the carrier disc 30 when the carrier disc rotates in one direction. However, in response to rotation of the carrier disc in the opposite direction, the actuating ring is free to slip with respect thereto. A dust shield 34 is mounted adjacent to the carrier disc and actuating ring.

The entire assembly is held in Place by means of a spring or bellville washer 35, a flat washer 36 and a retaining clip 37 which is received in an angular groove 38"provided adjacent to the end of the hub 16.

A U-shaped cover 39 is provided for the assembly and is atache'd to a mounting plate 40 on the motor 14 by means of screws 41 extending through the flanged portions 42. The cover 39 may also serve as a bracket for the purpose of mounting a safety device to a support portion 43 of the apparatus. Mounted within the cover 39, is an electrical switch assembly 44, which includes two contact carrying arms 45 and 46 which are suitably insulated from each other by an insulation pack 47. The contact arm 46, which is disposed most closely adjacent to the wall of the cover 39, has an extending portion 48 which projects beyond the length of the contact arm 45. The cont-act arm 46 is made of spring material so as to maintain the contacts in normally closed position.

The projection 48 on the contact arm 46 is disposed in the path of movement of an actuating arm 49 which is afiixed to the actuating ring 26, as at 50, for concurrent movement therewith. The range of movement of the actuating arm 49 is limited by its abutment with the wall of the cover 39 at one end and by its abutment with the projection 48 at its other end. By predetermining the length of the actuating arm 49, the maximum range of arcuaite movement of the actuating arm can be maintained to a desired degree.

The normally closed switch assembly 44 is disposed in the circuit to the heat lamp 13, as schematically indicated in FIG. 1. It will be apparent that the opening of the switch assembly, will cause the circuit to the heat lamp to be interrupted or opened.

In the operation of the safety control device, the synohronous motor 14 maintains a constant speed, for example, 30 r.p.m. at the motor shaft. This rotation of the motor shaft 15 is transmitted through the hub 16 to the inner race 19 of the planetary assembly 18. For purposes of example, it may be assumed that the reproduction equipment, which is to be controlled, has a variable speed range which is reflected in the rotation of the idler shaft 11 at 20-30 r.p.m. movement of the feed belt 12 should be decreased to a speed which is significantly less than the established operating range of the equipment, a hazardous condition can exist. As previously mentioned, when the feed belt 12 travels too slowly, it is exposed for too long a period of time to the intense heat of the heat source 13. This can cause injury to the belt itself, as well to the papers carried by the feed belt. Under some conditions, the speed of the belt may be reduced sufficiently to create a definite fire hazard.

In order to detect this type of malfunction in such reproduction equipment and to obviate the hazardous condition which may result therefrom, the safety control device 10 is designed to open the circuit to the heat lamp when the speed of the idler roll 11 drops significantly below 20 r.p.m., for example when it reaches 17 r.p.m. If the shaft 15 of the synchronous motor is rotating in a counter-clockwise direction and the pulley 23 is maintained stationary, it is characteristic of the planetary ball bearing assembly 18 that the balls 21 and the ball cage 22 will tend to move in a counter-clockwise orbit. However, if pulley 23 and the outer race 20 of the assembly are rotated in a clockwise direction, the orbital movement of the ball cage in the counter-clockwise direction is diminished and, at sufficiently high speeds of rotation of the pulley 23, is completely off-set and may even result in orbital rotation of the ball cage 22 in a clockwise direction. In the illustration given, the ratio between the pulleys 23 and 25 is so established that, when the pulley 25 on idler roll 11 is rotating at just above 17 r.p.m., the transmitted rotative speed of the pulley 23 is just sufiicient to overcome the counter-clockwise orbital movement of the ball cage 22 and thus maintain the balls and the ball cage in a position where no orbital rotation thereof occurs. This rotative speed of the pulleys 23 and 25 may be termed a critical speed or equilibrium speed because of the rotative forces im- If, for any reason, the

pressed upon the balls and the ball cage by the inner race 19 and the outer race 20 of the planetary assembly are such that the ball cage assembly is maintained in a condition of orbital equilibrium.

If the speed of the idler roll 11 should gradually and slowly drop below the critical or equilibrium speed, the ball cage assembly will slowly and gradually commence to have orbital rotation in a counter-clockwise direction. If the speed of the idler shaft 11 should drop suddenly, then the ball cage assembly will rotate much more rapidly in a counter-clockwise orb-ital movement. If, on the other hand, the speed of the idler shaft 11 is greater than the critical speed, then the ball cage assembly will be caused to rotate in a clockwise orbital movement. The speed of such orbital movement will be proportional to the speed of the idler roll 11, as translated to the pulley 23.

By means of the pins 27, any orbital movement of the ball cage 22 is transmitted into concurrent rotative movement of the carrier disc 30. By reason of the ball clutch assembly, such rotation of the carrier disc in a counterclockwise direction will be immediately transmitted to the actuating ring 26. However, if the rotation of the carrier disc 30 is in the opposite, clockwise direction, the actuating ring 26 can be maintained against corresponding rotative movement.

The operation of the device will now be described. If the feed belt 12 is travelling at a speed within the expected and established range, the idler roll 11 and its associated pulley 25 will be rotating at a speed between 20 and 30 r.p.m. This rotation will be transmitted through the belt 24 tothe pulley 23 on the safety control device and will result, in the manner previously described, in the orbital rotation of the ball cage 22 and the carrier disc 30 in a clockwise direction of movement. During this rotation, the actuating ring 26 will be urged in a like direction of rotation, but will be restrained against further rotation in such direction as soon as the upper end 51 of the actuating arm 49 abuts the adjacent wall of the cover 39. When the actuating arm is in this position, its lower end 52 is not in contact with the contact arm 46, but is disposed closely adjacent to the projection 48 on that contact arm. The contact arms 45 and 46 are in their normally closed position of engagement and the switch assembly 44 completes the circuit to the heat lamp 13. However, if for any reason, the speed of the feed belt 12 should be impeded or its movement should be momentarily arrested completely, so that the rotation of the idler roll 11 drops below the critical or equilibrium speed, this will be immediately reflected in counter-clockwise rotation of the actuating ring 26 which will cause the end 52 of the actuating arm 49 to move into engagement with the projection 48 which is disposed in the path of counter-clockwise movement of the actuating arm. This engagement will cause the contact arms 45 and 46 to become separated and thereby open the electrical circuit to. the heat lamp 13. The movement of the actuating ring and its actuating arm 49 will be arrested as soon as the movement of the contact arm 46 is arrested by abutment adjacent to the cover 39. When the range of arcuate movement of the switch actuating element 49 is extremely limited, as illustrated in the present instance, then the switch operating response of the safety control device 10 to the malfunction or under-speed condition is substantially instantaneous. The restraint on further movement of the actuating ring and the actuating arm creates an overload condition on the synchronous reference m0- tor 14 which causes it to stall. In this particular application of the safety control device, it is desirable that the operation of the drive motor of the reproduction apparatus not be interrupted, as continued movement of the feed belt 12, even at subnormal speed, can prevent injury resulting from the residual heat which is still existent even after the heat lamp is shut off.

The operator of the reproduction apparatus will immediately observe that the heat lamp has been extinguished, and will have to take appropriate steps to remedy the malfunction which resulted in the underspeed condition of the feed belt 12. As soon as the malfunction has been remedied, the feed belt 12 will be operating at its established speed. Thereby the actuating ring 26 and the arm 49 will be relieved of the counter-clockwise rotative force and will be urged by the spring pressure of the contact arm 46, as well as by the slight frictional force of the rotating'carrier disc 30, which should be rotating in a counter-clockwise direction, to its position where the upper end 51 of the actuating arm again abuts the cover 39; The .switch assembly 44 will again assume its normally closed position and the circuit to the heat lamp 13 will again be completed, permitting normal operation of the apparatus.

It is to be noted that the utilization of the ball clutch assembly 32-33 permits the safety control device to be responsive only to the underspeed condition of malfunction. It will be apparent however, that under the same conditions of rotation that have been described, the safety control device can be made responsive to an overspeed condition only 'by reversing the direction of engagement of the ball clutch and disposing the switch assembly 44 so that it is engaged by the upper end 51 of the actuating arm 49 instead of the lower end 52 thereof. In other words, the principal of the operation of the safety control device is applicable to either underspeed or overspeed response.

If the malfunction or underspeed condition is of a momentary character only, which is cured without any required attention from the operator of the apparatus, then the switch assembly 44 will automatically reset itself and restore the heat lamp circuit as soon as the idler shaft 11 has been restored to normal operating speed. There may even be applications of the safety control device, where it is not desirable that the operation of the apparatus be interrupted if the malfunction is only m'omentary. By shortening the length of the actuating arm 49 or otherwise enlarging the arcuate range of movement of the switch actuating element 49, the response of the safety control device 10 can be delayed so that momentary malfunction conditions will not induce sufiicient movement of the switch actuating element 49 to cause it to engage and open the switch assembly 44. However, if the malfunction is more than momentary, the switch actuating member 49 will persist in its switch opening movement and thus interrupt the electrical circuit in the manner previously described. However, the extent of movement of the actuating element 49 is only one factor in determining the speed of response of the safety control device 10. Another factor is the rate or speed at which the actuating element is moved. This factor is determined by the severity of the malfunction rather than by its duration. Thus, even if the actuating element 49 has a sufiicient extent of movement so as to create a two second time lag in the response of the safety control device when the speed of the idler roll 11 is reduced ten percent below the critical speed, the response of the safety control device may, nevertheless, be substantially instantaneous when the speed of the idler roll is suddenly reduced to, for example, 60% of the critical speed. The safety control device is therefore characterized by the capability of having a very rapid, substantially instantaneous, response to a severe condition of malfunction, while providing a predetermined time lag or time delay to a minimal or less aggravated condition of malfunction.

Although the rapidity of response of the safety control device can be established in the design of the device, under some circumstances it may be desirable to have an adjustable time delay or response arrangement. In FIGS. 4 and 5 of the drawings, I have shown a modified form of the safety control device in which such adjustability of the response is provided. In the modified form, the actuating arm 53 is made somewhat shorter than the previously actuating arm 49. A cylindrical abutment 54 is secured to the cover 39 by means of a screw 55 which extends through a slot 56 provided in the cover. When the screw is released, the cylindrical abutment 54 can be moved along the slot to various selected positions and then secured in the selected position. The variation in the location of the cylindrical abutment will determine the permissible range of arcuate movement of the actuating arm 53. If the cylindrical abutment is in the solid line position shown in FIG. 4, the degree of movement of the actuating arm 53 will be severely limited and the response of the safety control device will be substantially instantaneous, as it was in the form shown in FIG. 1. If, however, the abutment 54 is relocated by moving it along the slot 56 to one of the positions shown in phantom outline in FIG. 4, then the actuating arm 53 will have a greater degree of movement thus creating a time lag in the response of the safety control device to an underspeed condition. By using this modified form of the safety control device, the desired time lag or response period of the device need not be predetermined, but can be established at the point of application of the safety control device and can be determined empirically.

In FIG. 6, I have shown another modified form of the safety control device in which the reference speed synchronous motor 14 has been eliminated and, in lieu thereof, the constant speed shaft 57 of the safety control device is connected through pulley 58, belt 59 and pulley 60, to the shaft 61 of the electric motor (not shown) which drives the reproduction apparatus. The drive motor itself thus serves as the reference speed for the safety control device. It will be understood, that by selecting a proper ratio between the pulley 58 and the pulley 60, the desired speed at the shaft 57 can be obtained. In other respects, the safety control device operates in the manner previously described. However, inasmuch as the drive motor for the apparatus may be considerably more powerful than the synchronous motor 14 which has been previously described, it may not be feasible to stall the drive motor when the safety control device operates to open the switch assembly 44. Therefore, as shown in the schematic wearing diagram of FIG. 7, the circuit may be so arranged that the opening of the switch 44 will open the circuit to both the heat lamp 13 and the drive motor 62. Such a circuit will prevent any stalling or overloading of the motor 62. Such a circuit may likewise be used when the synchronous motor 14 is employed. This circuit does not automatically reset itself as is the case in the circuit shown in FIG. 1. After the malfunction has been remedied, the circuit is reestablished by means of the reset switch 63 which establishes a shut circuit until such time as the switch 44 closes.

Although the safety control device has been described as opening a normally closed switch, it will be readily apparent that the principle of operation of the device can be applied equally to a normally open switch by simply reversing the positions of the contact arms 45 and 46. It will also .be understood that I have described a simple form of single pole single throw switch 44, but that my invention is not limited to the use of such a switch but contemplates also the use of multiple pole multiple throw switch arrangements where such switches are considered necessary or desirable.

Although I have referred to the shaft 61 as being the motor drive shaft, it will be understood that such shaft could be any shaft directly associated with the drive motor 62.

It is to be understood that the forms of my invention, herewith shown and described, are to be taken as preferred examples of the same, and that variou changes may be made in the shape, size and arrangement of the parts thereof, without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. A speed-responsive safety control comprising: a driven rotary element whose speed variation is to be sensed, a rotary reference speed element correlated to the desired speed nange of the driven rotary element, a

planetary reduction mechanism interconnecting said elements in speed sen-sing relationship, a constant speed synchronous electrical motor, independent of said driven element, driving said reference speed element, said motor being characterized by the ability to be stalled under overload without injury to said motor or to said elements and mechanism, a clutch mechanism responsive solely to rotation in one direction, a switch-actuating element operatively connected to said planetary mechanism through said clutch mechanism for positive rotary actuating movement in said one direction responsive to a diflerential speed relationship between said driven element and said reference speed element, and means disposed in the path of said movement of said switch-actuating element for overloading said motor and arresting differential-speed responsive movement of said actuating element after said actuating element ha traversed a selected angularity of rotary movement to a switch-actuating position.

2. A speed-responsive safety control as defined in claim 1, including spring means yieldably opposing said movement of said actuating element into switch-actuating position.

3. In a speed-responsive safety control the combination of a driven rotary "element whose speed variation is to be sensed, a rotary reference speed element correlated to the desired speed range of the driven rotary element, a planetary reduction mechanism interconnecting said elements in speed sensing relationship, a switch-actuating ele ment operatively connected to said planetary mechanism for arcuate switch-actuating movement responsive to a differential speed relationship between said driven element and said reference speed element, a pair of spaced ra-but ments disposed in the path of movement of said switchactuating element and limiting the arcuate travel thereof, means mounting at least one of said abutrnents for selective movement relatively to the other of said abutments to adjustably vary the limits of arcuate movement of said switch-actuating element.

I References Cited by the Examiner UNITED STATES PATENTS 2,046,283 6/1936 Berlyn 192-150 2,723,686 11/1955 Durash 139336 2,753,969 7/1956 Chung 192150 2,782,902 2/1957 Sloane 198-20 3 2,843,691 7/ 1958 Champion et a1. 2006-l.46 2,901,076 8/1959 Dean 192-150 KATHLEEN H. CLAFFY, Primary Examiner.

ORIS L. vRADER, ROBERT K. SCHAEFER, Examiners 

1. A SPEED-RESPONSIVE SAFETY CONTROL COMPRISING: A DRVIEN ROTARY ELEMENT WHOSE SPEED VARIATION IS TO BE SENSED, A ROTARY REFERENCE SPEED ELEMENT CORRELATED TO THE DESIRED SPEED RANGE OF THE DRIVEN ROTARY ELEMENT, A PLANETARY RUDUCTION MECHANSIM INTERCONNECTING SAID ELEMENTS IN SPEED SENSING RELATIONSHIP, A CONSTANT SPEED SYNCHRONOUS ELECTRICAL MOTRO, INDEPENDENT OF SAID DRIVEN ELEMENT, DRIVING SAID REFERENCE SPEED ELEMENT, SAID MOTOR BEING CHARACTERIZED BY THE ABILITY TO BE STALLED UNDER OVERLOAD WITHOUT INJURY TO SAID MOTOR OR TO SAID ELEMENTS AND MECHANISM, A CLUTCH MECHANISM RESPONSIVE SOLELY TO ROTATION IN ONE DIRECTION, A SWITCH-ACTUATING ELEMENT OPERA- 